Risers are long tubular structures assembled from steel pipe. In service they are subjected to high dynamic loads and since service lives in excess of 20 years are often required fatigue is an important design issue.
Monitoring the varying stresses in the riser is an important requirement to provide input to a planned integrity management program. Historically strain gauges have been used but their reliability in deep water has been poor due to water ingress and problems associated with reliable bonding of the gauges to the pipe wall which can often be hot and subject to corrosion.